Electrical Impedance Tomography in the Assessment of Extravascular Lung Water in Noncardiogenic Acute Respiratory Failure: Materials and Methods

In: Respiratory Failure

26 Sep 2014

The study was performed at the ICU of the Saint Lucas Hospital in Apeldoorn, The Netherlands. Fourteen consecutive patients with a clinical diagnosis of noncardiogenic ARF were included in the study. The diagnosis was based on the presence of respiratory distress associated with dyspnea and tachypnea, hypoxemia, and bilateral and diffuse opacities on the chest roentgenogram in the absence of an elevated pulmonary capillary wedge pressure. Patients received mechanical ventilation with pressure control ventilation (Servo 900C; Siemens-Elema AB; Solna, Sweden). The levels of positive end-expiratory pressure (PEEP) and fraction of inspired oxygen (Fio2) were chosen according to clinical requirements. According to the lung injury score (LIS), patients were divided into two groups. The LIS was computed as described by Murray and coworkers using the number of quadrants involved on the chest roentgenogram, the Pao2/Flo2 ratio, the level of PEEP, and the quasi-static compliance (measured as Vt divided by inspiratory plateau pressure minus total end-expiratory pressure); each scored from zero to four. The mean of the scores gives the LIS. Patients with a score > 2.5 were defined as having ARDS. Patients with a LIS < 2.5 were defined as having acute lung injury (ALI). Patients with a history of chronic pulmonary disease were excluded because the impedance signal may be confounded by relatively poorly ventilated areas in emphysematous lungs. Patients were in a supine position. The protocol was approved by the local ethics committee, and informed consent was obtained from the closest relative of each patient. canadian family pharmacy online

After inclusion in the study, a fiberoptic catheter was placed in the femoral artery for the detection of EVLW by TDD. Afterwards, 16 electrodes were attached at the third intercostal level, and two EIT measurements were performed. During the measurements, the PEEP level and the Vt were kept constant. Within 10 min after the EIT measurements, one EVLW measurement with TDD was performed. All of the described measurements were repeated daily until any one of the following occurred: the patient died, EVLW became < 10 mL/kg, or the fiberoptic catheter could not receive an accurate signal anymore due to damage.

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